Emperor Taizong of Tang (r. 626–649) of Tang Dynasty China, after subjugating the Eastern Turkic Khaganate, begins to exert his military power toward the Western Regions, at this time dominated by the Western Turkic Khaganate as well as a number of city-states loosely allied with the Western Turkic Khaganate.

In the year 640, Emperor Taizong sends the military commander Hou Junji to defeat and annex Gaochang—the first attempt by any Chinese dynasty to set up permanent military and political presence in the region since Fú Jiān in the 4th Century.

In 644, after Yanqi—an ally in the campaign against Gaochang—turns against Tang and allies with the Western Turkic Khaganate, Tang's commandant at Gaochang, Guo Xiaoke, attacks and captures Yanqi's king Long Tuqizhi, but Yanqi subsequently breaks away again.

In 648, the ethnically Turkic Tang general Ashina She'e, who is the second son of Shibi Khan, attacks both Yanqi (Karasahr) and Qiuzi (Kucha in modern Aksu Prefecture, Xinjiang), conquering both.

Both Shule and Yutian then also submit to Tang, allowing the Tang Dynasty to dominate the region until it is briefly seized by Tufan (Tibet) during the reign of Emperor Taizong's son Emperor Gaozong.